Fix issues with XML export for New York Congressional elections

[lmullen]

• Some files fail to export with an error.
• Some counties appear not to be correct (perhaps my assumption that towns are always contained in counties is false).
• Town and county fields should be filled in even for records where there was no vote for the person.
• Add election ID.

[lmullen]

Some of the Congressional elections have no records for towns. For instance: ny.uscongress6.1789.xml

[lmullen]

Some of the Congressional elections have records for towns, but it only lists that there are towns, with no record of the votes for the towns. For example: ny.uscongress16.1806.xml

[lmullen]

A better strategy for finding counties: create a separate town and county data frame, only if the unit passed to the script is town, then join that to the votes data frame.